The present invention relates to an exhaust element of the type including a main exhaust pipe and a bypass mounted in parallel with the main pipe, which bypass includes a heat exchanger, and in which are arranged moveable means for shutting off the main pipe and moveable means for regulating the cross section offered for the gases to pass in the bypass.
Such an exhaust element is described, for example, in the European patent EP-B-0.058.842.
This exhaust element is intended to take up the heat from the exhaust gases coming from the internal-combustion engine of a motor vehicle so as to transfer this heat into the liquid cooling circuit of the engine.
This thermal transfer is particularly useful when starting up the vehicle from cold, so as to make it possible rapidly to obtain a substantial temperature in the liquid-cooling circuit of the engine. This is because this circuit for cooling the engine is also used for heating the passenger compartment of the vehicle.
Hence, it is known, by virtue of the means for shutting off the main exhaust pipe, to force the exhaust gases to flow through the bypass enclosing the heat exchanger. Moreover, it is known, so as to promote the heat exchange, to adjust the pressure in order to increase the temperature of the gases in the exchanger by virtue of the means for regulating the cross section offered for the exhaust gases to pass in the bypass.
In the known devices described particularly in the patent EP-B-0.058.842, the means for shutting off the main pipe are formed by a valve arranged in the main pipe. The means for regulating the passage cross section are formed by a three-way valve arranged in the bypass. The latter includes two separate sub-paths offered selectively for the exhaust gases to pass on the basis of the position of the three-way valve.
The valve arranged in the main pipe and the three-way valve provided in the bypass are controlled independently of one another by two separate actuators.
The structure of the exhaust element is thus complex to produce industrially, and the exhaust element requires several actuators to be used to control it.